The present invention relates to a spark plug for internal combustion engines.
Spark plugs heretofore known in the art have been generally of the type including a center electrode and a ground electrode which define a spark gap therebetween. Then, in recent years there has existed, for the purpose of improving the performance of an internal combustion engine (hereinafter referred to as an engine), a demand for improving the ignition performance through the realization of a higher compression ratio, the use of a lean-burn system, the installation of a turbocharger, etc., and attempts have been made to use wider spark gaps. Therefore, the plug voltage required has been going on increasing.
Measures heretofore proposed for the purpose of reducing the plug voltage required include for example means of decreasing the electrodes in diameter and this causes an increased in the electrode consumption and deterioration in the electrode durability. Thus, while means of forming the electrode tips with less-consumable platinum may be conceived, this means is also disadvantageous from the cost point of view.